A high frequency output is generally selected based upon the kind of heating load in carrying out high frequency heating and cooking. In other words, the high frequency output selected is dependent upon the constituent materials or substances of the heating load. In addition, cooking time is determined by the high frequency output selected and the weight of the heating load. Therefore, while preparing the heating load and consulting a cookbook, the user may select, calculate or determine the high frequency output and heating time in view of the kind and weight of the heating load. The cookbook generally discusses a full range of high frequency outputs and cooking times appropriate to all of the different kinds and weights of the heating loads which have been derived from preliminary or well established experiments. It is customary practice to enter those appropriate high frequency outputs and cooking times on a keyboard of the appliance. The conventional appliance requires a very complicated procedure and results in an increased possibility of faulty operation and inconvenience in use.
To accommodate a variety of different kinds of heating loads, a full range of high frequency outputs and cooking times, a microcomputer is programmed to permit all possible combinations of high frequency outputs and heating times to be established. As a result, the capacity of an ROM in the microcomputer must be very large.
A sample is illustrated in FIG. 1 which shows some examples of poultry often cooked in American homes. There are three kinds of poultry which are widely cooked in American homes: Cornish hen, chicken and turkey. It is appreciated that the high frequency outputs and heating times which are necessary to cook those kinds of poultry are as follows:
______________________________________ Cornish hen 700 W 7 min/0.45 kg (FIG. 1A) Chicken 700 W 6 min/0.45 kg (FIG. 1B) Turkey 490 W 5 min/0.45 kg (FIG. 1C) ______________________________________
The relationships among the weight of the heating load, the heating time and the high frequency output in those cases are depicted in FIGS. 1A, 1B and 1C. Having consulting a cookbook beginning with the major classes of heating loads (in the example given, fowl) and then the sub-classes thereof (in the example given, Cornish hen, chicken and turkey), the user of the conventional appliance finds the optimum value of high frequency output and that of heating time from the book and introduces these values through high frequency output setting pads and heating time setting pads. Furthermore, the user should calculate the heating time setting by multiplying the weight of the heating load by a unit time as shown in the book. In the conventional method, it is impossible to introduce high frequency output and heating time settings without following a complex procedure. The user also feels the inconvenience in use.
An improved high frequency heating appliance of which a flow chart is illustrated in FIG. 2 has been suggested. The heating load is grouped into major classes and subclasses as follows:
______________________________________ Major class 1 . . . beef 2 . . . pork 3 . . . poultry Sub-class 3-1 . . . Cornish hen 3-2 . . . Chicken 3-3 . . . Turkey ______________________________________
When it is desired to effect high frequency heating on the sub-class "turkey", "major class key 1" characteristic of poultry, "sub-class key 3" characteristic of turkey and weight keys characteristic of a weight (w) are sequentially pressed. As a result, the heating time is computed and the high frequency output is selected automatically to carry out automated heating processes.
In the above conventional method, because of no linear relationship between weight and optimum cooking time, there are established several weight brackets having its unique constants assigned thereto assure approximate values of heating time. The weight brackets are usually equally spaced and, for example, every 2 kg against a maximum of 6 kg. A total of 18 constants determinative of weight-to-time relationship a.sub.1, a.sub.12, a.sub.13, a.sub.2 . . . a.sub.53, b.sub.1, b.sub.12 . . . b.sub.52 are required since the same weight brackets apply to the sub-class. A greater number of the major classes or sub-classes would cause a remarkable increase in the number of the constants and therefore the needed capacity of an ROM contained in a microcomputer.